1. Technical Field
Various embodiments generally relate to a semiconductor device. More particularly, the embodiments relate to a semiconductor device including a memory block and method of operating the same.
2. Related Art
A memory block of a NAND flash memory device includes a drain select transistor, memory cells, and a source select transistor. The drain select transistor, memory cells, and a source select transistor are connected between a bit line and a common source line. The select transistors may be formed to have the same structure as the memory cells. Accordingly, the select transistors should have a predetermined threshold voltage in order to operate like a conventional transistor. The threshold voltages of the select transistors may be controlled by a program operation. However, when the program operation is repeatedly performed on the select transistors in which the threshold voltages are lower than a target level, the threshold voltages of the select transistors in which the threshold voltages reach the target voltage in advance are further increased. Accordingly, since threshold voltage distribution of the select transistors is wide, an operation error may occur.